1. Field of the Invention
The present invention relates to a technique of counting the number of passing objects to be counted in a path.
2. Description of the Background Art
Conventionally, various methods of detecting passing of an object to be counted such as a person in a path and counting the number of passing times have been proposed.
As an example, there is a known method of disposing a projecting unit for projecting a light beam and a light receiving unit for receiving the light beam while sandwiching a path and detecting passing of a person by using property that a person interrupts a light beam when the person passes the path.
Another known method is a method of emitting a slit ray in the width direction of a path, photographing an area of the position to be irradiated with the slit ray to obtain a two-dimensional image, analyzing the shape of an image of the slit ray in the two-dimensional image, and detecting passage of a person.
The method of disposing a light projecting unit and a light receiving unit while sandwiching a path and detecting passage of a person can be applied to a case where an object to be counted passes one by one like in an automatic checking and collecting machine. In this method, however, in the case where a plurality of objects to be counted are lined in the width direction of the path and pass between the units simultaneously, passage of each of the plurality of objects to be counted cannot be detected.
On the other hand, in the method of detecting passage of a person on the basis of the shape of an image of a slit ray in a two-dimensional image, even when a plurality of objects to be counted pass between the units simultaneously, the passage of each of the plurality of objects can be detected. However, the whole two-dimensional image has to be computed to analyze the shape of the image of the slit ray, so that the computation load is relatively heavy. As a result, the counting process cannot be performed at high speed and it is feared that a counting error occurs.